This study will measure the changes in antibody levels for staphylococcal proteins, superantigens, type II collagen, and tetanus in rheumatoid arthritis patients during treatment with the protein A column as well as analyze the ability of serum, pheresis affluent, and pheresis effluents from RA patients during treatment with the protein A column to produce and/or inhibit superantigen-induced mitogenic lymphocyte proliferation.